moments_xld — Geometric moments M20, M02, and M11 of contours or polygons.
moments_xld calculates the moments (M20, M02, and M11) of the region enclosed by the contours or polygons XLD. See moments_region_2nd for the definition of these features. The moments are computed by applying Green's theorem using only the points on the contour or polygon, i.e., no region is generated explicitly for the purpose of calculating the features. It is assumed that the contours or polygons are closed. If this is not the case moments_xld will artificially close the contours or polygons.
It should be noted that moments_xld only returns useful results if the contour or polygon encloses a region in the plane. In particular, the contour or polygon must not intersect itself. This is particularly important if open contours or polygons are passed because they are closed automatically, which can produce a self-intersection. To test whether the contours or polygons intersect themselves, test_self_intersection_xld can be used. If the contour or polygon intersects itself, useful values for the moments can be calculated with moments_points_xld.
If more than one contour or polygon is passed, the results are stored in tuples in the same order as the respective contours or polygons in XLD.
Contours or polygons to be examined.
Mixed second order moment.
Second order moment along the row axis.
Second order moment along the column axis.
Let n be the number of points of the contour or polygon. Then the run time is O(n).
moments_xld returns 2 (H_MSG_TRUE) if the input is not empty. If the input is empty the behavior can be set via set_system(::'no_object_result',<Result>:). If necessary, an exception is raised.
gen_contours_skeleton_xld, smooth_contours_xld, gen_polygons_xld
moments_any_xld, moments_points_xld, moments_any_points_xld
moments_any_xld, area_center_xld, moments_region_2nd, area_center